The present invention relates generally to apparatus for filtering debris from a moving airstream and, more particularly, to air filtration apparatus for use in cleaning lint and dust laden air within textile mills.
In textile mills and other similar industrial settings where airborne lint, dust and other debris can be problematic, it is common practice to filter the ambient air on a continuing basis, one typical filtration system arrangement utilizing a series of filtration units of increasing efficiency. In filtration systems of this type, the initial filtration unit is commonly referred to as a prefilter or a rough filter in that the unit is equipped with a relatively coarse filtering media adapted primarily to remove larger pieces of lint and like fibrous debris and other relatively heavy dust and debris particles but not to completely clean the airstream passing through the filter.
One of the most common forms of such prefilters or rough filters is a so-called rotary disk filter wherein a circular filter element is rotatably supported within a correspondingly circular airflow opening in an otherwise impervious filter frame wall for axial airflow through the circular filter element. While it is considered to be desirable to maintain some accumulation of separated lint and debris on the filter element to enhance its filtration efficiency, excessive build-up of lint and debris is equally undesirable and, accordingly, prefilters are characteristically provided with some means for at least periodically removing a portion of the lint and debris accumulation from the filter medium. For this purpose, rotary disk-type prefilters may be equipped at the so-called dirty side of the filter element with a stationary suction nozzle having an elongated intake slot extending the full radius of the filter element to continuously withdraw accumulated lint and debris from the filter element as it rotates during operation.
While suction cleaning nozzles of this type are generally effective for their intended purpose in the operation of rotary disk prefilters, they suffer the disadvantage that a relatively powerful fan motor must be provided to exert sufficient suction along the entire length of the intake slot in order to achieve acceptable cleaning of the filter element over its entire radius and surface area and, therefore, such filter cleaning arrangements do not always achieve an optimal degree of cleaning efficiency which, in turn, can make it difficult to maintain a desirable pressure drop across the filter element and ultimately results in a shorter filter element life.